I have many years experience GMing many different games ranging from D&D to Shadowrun. I prefer to GM over playing as I view it as an art form to share with players who can interact with the game and have a major influence upon the game world. The interaction between the players and the game world is what makes roleplaying really worthwhile. If the players can say by the end of the game session that they had fun, then I have received my reward for doing a great job of GMing.